PLATE XXIV. 

 Fig. a. 



(Sp. No. 22968. "Without analyzer, x 18.) 



Schistose rhyolite-porphyry with well-developed flowage structure. A feldspar phenocryst 

 •which has been more or less rounded by crushing, occupies the center of the figure. There is also 

 shown iu the upper left-hand quadrant of the figure a small crushed quartz phenocryst. (Described, 

 p. 93.) 



Fig. R 



(Sp. No. 22968. "With analyzer, x 18.) 



"When the section represented in fig. A is viewed between crossed iiicols, the crushed character 

 of the feldspar phenocrysts is thereby well brought out. The minutely granular character of the 

 grouudmass is also well shown. (Described, p. 93.) 



278 



